Wait, so how is it fitting properly? 28*13 = 364, but I don't see a day missing. What am I not understanding?

Jeez, lol. Sorry about that :)

It appears to have 30 days in October and 31 days in November.

Sorry about that. The perils of artisanal calendaring.

https://i.imgur.com/AoH5A67.png

I think you're missing August 13th. As the other commenter pointed out, 13*28 = 264.

I think you may have a point.

Not that big of a deal though. I have nothing planned for that day :)

Thanks, you found it! I was going nuts.

What happens on leap years?

You get an extra cell in the last column.